The X-ray CT (Computed Tomography) device including an X-ray source for irradiating the subject with X-ray, and an X-ray detector located opposite the X-ray source for detecting the X-ray penetrating through the subject is configured to reconstruct the difference in the X-ray attenuation rate inside of the subject as an image by the data processing system based on projection data in a plurality of directions derived from rotary imaging of the area surrounding the subject. Generally, the X-ray tube is employed as the X-ray source, which irradiates the electrode with electron accelerated at high voltage for emitting the X-ray through bremsstrahlung phenomenon. In order to pick up the image over a wide range at higher speeds at a time, the X-ray detector is configured by arranging the X-ray detection elements each formed as the combination of scintillator and photodiode in a two-dimensional array.
The dual energy imaging method as one of methods for imaging the subject using a plurality of different energies is the technique for obtaining the substance composition information utilizing energy dependency of the X-ray attenuation coefficient by imaging the same subject at two types of tube voltages.